The invention relates to an arrangement for introducing an elongate, flexible element, such as a drainage element, in particular a drainage ribbon, into a subsoil.
Such arrangements are for instance employed for consolidating a slack, water-bearing subsoil by stimulated or forced drainage. The drainage ribbons have a water transporting construction or composition and are vertically inserted into the subsoil, whereby the water is more rapidly drained upwards. The subsoil consolidates then more rapidly and the bearing strength of the subsoil increases.
It is common use to introduce drainage ribbons into the subsoil by means of a hollow mandrel that is kept upright by means of a king post and that is vertically driven into and out of the subsoil while leaving the drainage ribbon behind that is fed through the hollow mandrel. The end of the introduced drainage ribbon is initially anchored into the subsoil by means of an elongate push bar. The push bar extends through the entire mandrel to be operated by an hydraulic cylinder at the top of the mandrel.
In practice, the bottom end of the mandrel undergoes the most wear due to the friction with solid particles in the subsoil. When the bottom of the known mandrel has worn out, the entire mandrel is replaced. This requires that the push bar is drawn out of the entire mandrel, which can only be performed with the king post laying horizontally. Therefore in practice the replacement of the mandrel is avoided by employing for each new drainage project a mandrel that has well enough reserve for that project, as a replacement operation may last multiple working days and it is impractical to ship a new mandrel to the project area due to its length. The employment of mandrels with well enough reserve to be on the safe side implies that mandrels are decommissioned before the technical lifetime has passed. This is disadvantageous from a cost perspective.
It is an object of the present invention to provide an arrangement for vertically introducing an elongate, flexible element into a subsoil by means of a hollow mandrel, wherein the technical lifetime of the mandrel can be optimized.